The present invention relates to a light source using light emitting diode (LED) devices and a liquid crystal display apparatus using the light source as backlight.
Light emitting diode (LED) devices are being applied to liquid crystal display apparatuses gradually but the light emission efficiency thereof does not yet reach the level at which the requirement therefor is satisfied sufficiently. In order to improve the light emission efficiency, high refractive index material is used as resin material in peripheral part and the reflection factor of material for a reflecting plate of a package is improved. However, the external quantum efficiency of the LED device is usually as small as 20 to 30% and further improvement is required. The structure of improving the light taking-out efficiency of the LED device itself is important since the light emission efficiency can be improved directly.
Publicly known techniques of improving the light taking-out efficiency of the LED device constituting light sources of illumination apparatuses and backlight modules of the liquid crystal display apparatuses are described below.
In prior art technique, JP-A-2006-210730 discloses a light taking-out groove formed in LED device. This publication describes the groove formed to prescribe the range of an inclination angle to take out light effectively, so that light is emitted from divided light emission areas to the outside efficiently.
Moreover, JP-A-2006-196543 and JP-A-2006-210961 describe uneven structure formed in a substrate in which crystal grows or in light transmissible electrode provided on the surface of crystal. Transmission light is obtained efficiently as diffuse light in the uneven structure formed in an interface of the substrate or the surface electrode without limited to the total reflection angle of the interface.